Work-related musculoskeletal disorders (WMSD) account for 1 in 3 lost work time illnesses. In spite of epidemiological evidence for a positive relationship between exposures to repetitive and/or forceful motion and the prevalence and incidence of WMSD, the mechanisms of pathophysiology are incompletely understood. In our previous grant, we explored the short-term effects (3-12 weeks) of such tasks on inflammation and motor behavior, and found that higher demand tasks lead to a cyclical inflammation response with motor declines. Our goal in this competitive renewal is to use our highly innovative and unique animal model of WMSD to identify and characterize cellular mechanisms underlying inflammatory tissue changes associated with long-term performance (18 and 24 weeks) of repetitive and/or forceful reaching. SPECIFIC AIM 1) To determine the extent to which long-term exposure to 2 task regimens, low repetition-low force (LRLF), and high repetition-low force (HRLF) causes tissue changes indicative of inflammation. Specific Aim 2) To determine the extent to which long-term exposure to 2 task regimens (LRLF and HRLF) causes motor behavior changes indicative of inflammation. These proposed experiments are vital for full understanding of the effects of long-term exposure to combinations of risk factors on tissue and motor function, as well as immune cellular mechanisms underlying the inflammatory tissue responses. The data generated by these studies will ultimately contribute to the development of new strategies for effective prevention and management of WMSD.